1. Field of the Invention
The present invention relates to zoom lenses, especially to zoom lenses with low cost, high zoom ratio, small size, and good image quality.
2. Description of Related Art
Image-capturing devices, such as digital cameras or digital camcorders, employ a zoom lens and an image sensor to collect an image beam from an object, in which the zoom lens focuses the image beam on the image sensor, which then turns the analog signals of the image beam into digital signals for following processing, transmitting, and storage.
Typically, the zoom lens of the image-capturing devices consists of several lens groups. A zoom lens with less lens groups typically has lower cost and little dimension. In addition, plastic lenses are usually used to replace the glass lenses for further reducing the weight and cost. The plastic lenses, however, are sensitive to temperature. For compensating the temperature effect during the zooming, the displacements of the plastic lenses are typically larger than the glass lenses. The dimension of the zoom lens is therefore inevitably increased. Further, if too many plastic lenses are employed in a zoom lens, the image quality is usually unsatisfactory.
Therefore, it would be advantageous to provide novel zoom lenses having advantages of low cost and compact size as well as good image quality.